1. Field of the Invention
The present invention relates to a paper sheet stacking apparatus to be applied to, for example, a banknote sorting machine for sorting banknotes (hereinafter, referred to as paper sheets) according their denominations and the like.
2. Description of the Related Art
In a banknote sorting machine, paper sheets are taken in one by one by a take-in unit, conveyed via a conveyance path, inspected at an inspection unit, and, according to the result of the inspection, sorted and stacked in a stacking apparatus.
As a stacking apparatus, there has been known, for example, one disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-193517. More specifically, the stacking apparatus, as shown in FIG. 7, includes a first pair of conveying belts 101 that accepts paper sheets supplied along a conveyance path to pinch and feed the paper sheets, and second pairs of conveying belts 102 that are arranged at both the sides of the first pair of conveying belts 101 with a predetermined distance parallel to each other. Further, the stacking apparatus includes an impeller 104 that introduces paper sheets taken out from the first pair of conveying belts 101 and the second pairs of conveying belts 102 into between vanes 103 to guide the paper sheets in a predetermined direction in slowdown and discharges the paper sheets, and a stack housing that stacks the paper sheets discharged from the impeller 104.
The first pair of conveying belts 101 is configured by an upper belt 101a and a lower belt 101b, and the second pair of conveying belts 102 is configured by an upper belt 102a and a lower belt 102b. The upper belts 101a, 102a are stretched over rollers 105, 106 and released upward.
However, in the prior art, a paper sheet P has been conveyed to a passing area to the impeller 104 by three belts, i.e., the upper belt 101a of the first pair of conveying belts 101 and the upper belts 102a, 102a of the second pairs of conveying belts 102. Consequently, a force of binding the paper sheet P by the upper belts 101a, 102a, 102a is strong. If the paper sheet P is fed, for example, in its skewed state, the paper sheet gains entry into the vanes 103 as it is in the skewed state.
For this reason, as shown in FIG. 8, the paper sheets cannot gain entry into the vanes 103 of a same phase of impellers 104a, 104b that are positioned in the front side and the back side, respectively, but the paper sheets get alternately into vanes 103 of different phases, which causes a stack failure.
Further, even when the paper sheet P is conveyed in a non-skewed state, in particular, in the case where the speed of conveying the paper sheet P is increased in order to increase the processing capacity, the impact at the moment when the paper sheet P collides against the vanes 103 becomes large, and the paper sheet P becomes buckled as shown in FIG. 9, which causes a stack failure.
The present invention has been made in consideration of the above circumstances, and accordingly, an object of the present invention is to provide a paper sheet stacking apparatus in which, if a paper sheet entering an impeller is skewed, the skewed state can be corrected, and the impact when the paper sheet enters the impeller can be buffered.